In the employment of burners driven by a fuel and pure oxygen, so-called oxy-fuel burners, a higher flame temperature and smaller volumes of exhaust gas will be obtained than in burners operated using a fuel and air or oxygen-enriched air. High flame temperatures are a primary objective in high temperature processes, for instance in melting steel in light arc furnaces, or in order to achieve high thermal transmission, i.e. to increase output capacity because of more rapid heating rise times. Small volumes of exhaust gases give correspondingly small thermal losses, since these are a function of the volume of exhaust gas and the temperature of the exhaust gas. A burner which is operated using oxygen gives a flame temperature of approximately 2,800.degree. C. and a volume of exhaust gas of approximately 3 Nm.sup.3 /kg of fuel, while a burner operating with air gives a flame temperature of approximately 1,900.degree. C. and a volume of exhaust gas of approximately 12 Nm.sup.3 /kg of fuel using, for example, heating oil as fuel. Hence, oxy-fuel burners have a high degree of thermal efficiency.
However, in certain physical applications it may be difficult to extract the full benefit of the high flame temperature of oxy-fuel burners, for example in heating furnaces where the high flame temperature may result in considerable variations and uneven heating of matter because of locally extreme heating.
One object of the present invention is, hence, to realize a method for reducing the flame temperature of an oxy-fuel burner without thereby occasioning considerable increase in the volume of exhaust gas produced.
A further object of the present invention is to device an oxy-fuel burner which, in operation, gives a lower flame temperature than standard oxy-fuel burners.